A wind turbine known in the art typically comprises a wind turbine tower and a wind turbine nacelle positioned on top of the tower. A wind turbine rotor, comprising three wind turbine blades, is connected to the nacelle through a low speed shaft, which extends out of the nacelle front as illustrated on FIG. 1.
In recent years the development of mass-produced wind turbines has moved towards making them larger and larger, both in output and in size. This process calls for better and more cost-efficient components and manufacturing methods, and particularly in the field of mass-produced wind turbine blades, this development has been profound, in that the average mass-produced wind turbine blade over the recent years has more than doubled its length.
Wind turbine blades known in the art are typically made of fibre-glass reinforced by metal, wood or carbon fibres. The blades are typically manufactured by moulding two blade halves in two independent moulds and when the blade halves are hardened the two are connected to form the wind turbine blade.
To ensure the aerodynamic properties of an operating wind turbine blade it is important that the blade is substantially rigid and substantially do not change shape e.g. when subject to a high wind load, centrifugal force, gravity or other.
However it is also important that the blade is a little flexible so that the blade can bend a little when subject to sudden wind gusts or other.
Fibres running in the longitudinal length of the blade is a very efficient way of providing the blade with the desired qualities regarding stiffness and flexure but for a fibre to be able to affect the blades rigidity noticeably, it first of all has to be rigidly connected to or integrated in the blade and second of all it has to run continuous and substantially straight (i.e. without creases and wrinkles) in the entire length of the fibre, especially if it has to extend substantially in the entire longitudinal length of the wind turbine blade.
However, a single fibre is so flexible that it would be virtually impossible to ensure no creases or wrinkles while the fibre is attached to the rest of the blade.
E.g. from US patent no. 2007/0140861 A1 it is therefore known to form a stiff board of longitudinal extending fibres and then places this specially adapted board in the blade shell to reinforce the blade.
However this board would have to be made with a low tolerance to fit the shell and it would only fit a specific blade type.
An object of the invention is therefore to provide for an advantageous technique for reinforcing a wind turbine blade.